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by evdev 3351 days ago
IMO the hierarchy of need for this goes:

1 - case classes / value classes / data classes, whatever you want to call them.

2 - match-and-bind syntax

...

11? - fancy pattern matching

This maybe says more about how much I pay attention to what's upstream in Java, but I found the fact that this is just a hypothetical proposal, in April of 2017, strangely shocking. I guess I figured it had to be on the docket for a future java version already.
3 comments
aardvark179 3351 days ago
This is not just a hypothetical proposal, I believe there is a working prototype and a lot of thought has gone into this. More things are coming, but pattern matching is a low hanging fruit that doesn't have difficult interactions with the type system or VM. Value classes need a lot of language enhancement to be really useful, and those things are likely to land before value classes themselves.
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pdpi 3351 days ago
Project Valhalla (featuring value classes) is scheduled for Java 10 — so it'll probably arrive in production around 2020.
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aardvark179 3351 days ago
I cannot comment on the Java release schedule, but Project Valhalla will be done when it's done, and it is not a small task. Project Amber is intended for smaller changes that may have been investigated as part of Valhalla and can be released earlier.
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chairmanwow 3351 days ago
Maybe I'm misunderstanding your comment, but aren't case classes a fundamental piece of pattern matching? Or are you rather just suggesting the importance of which kinds of pattern matching are the most important?
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evdev 3351 days ago
match { case v: java.util.Date => }

This still works without case class extractors and is useful. That's what I mean by matching and binding.

Extracting/destructuring in the match statement can sometimes be more trouble than it's worth. It's definitely brittle to changes in the case classes. Then there's the question of the (difficult to reason about?) cost of the abstraction.

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hasenj 3351 days ago
I think some/most of the "needed" features for Java are already available in some other JVM languages. I'm not too familiar with the JVM ecosystem but Kotlin comes to mind.
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